Lymphopoietin

Lymphopoietin is a historical or umbrella term used to describe cytokines that promote lymphocyte production and growth. In early immunology, lymphopoietin referred to soluble factors capable of stimulating lymphoid cells, particularly during development in the bone marrow and thymus. The term does not correspond to a single defined molecule in modern nomenclature.

Today, the best-characterized molecule associated with lymphopoietic activity is interleukin-7 (IL-7). IL-7 is produced mainly by stromal cells in the bone marrow and thymus and acts on lymphoid progenitors and developing thymocytes to promote survival, proliferation, and differentiation. It signals through the IL-7 receptor, which comprises the IL-7R alpha chain and the common gamma chain, activating JAK-STAT pathways to support lymphopoiesis. IL-7 also contributes to the homeostasis of mature T cells and B cells under certain conditions.

Clinical and research interest in lymphopoietin-related activity centers on immunodeficiency and immune reconstitution. Exogenous IL-7 has been studied as a means to enhance T-cell reconstitution after bone marrow transplantation, HIV infection, or chemotherapy, and to expand naive T-cell pools. Because it specifically targets lymphoid development, therapeutics aiming at lymphopoietin pathways must balance immune restoration with risks of lymphoproliferation or autoimmunity. The term "lymphopoietin" is now rarely used in favor of identifying the precise cytokine involved.